Avoid the Vec reversal in DisplayList::hit_test.

components/gfx/display_list/mod.rs

@@ -480,9 +480,8 @@ impl DisplayList {
             &draw_target, &stacking_context.filters, stacking_context.blend_mode);
     }
 
-    /// Places all nodes containing the point of interest into `result`, topmost first. Respects
-    /// the `pointer-events` CSS property If `topmost_only` is true, stops after placing one node
-    /// into the list. `result` must be empty upon entry to this function.
+    /// Return all nodes containing the point of interest, bottommost first,
+    /// and respecting the `pointer-events` CSS property.
     pub fn hit_test(&self, point: &Point2D<Au>, scroll_offsets: &ScrollOffsetMap)
                     -> Vec<DisplayItemMetadata> {
         let mut traversal = DisplayListTraversal {
@@ -492,7 +491,6 @@ impl DisplayList {
         };
         let mut result = Vec::new();
         self.root_stacking_context.hit_test(&mut traversal, point, scroll_offsets, &mut result);
-        result.reverse();
         result
     }
 }

components/layout/query.rs

@@ -150,6 +150,7 @@ impl LayoutRPC for LayoutRPCImpl {
         };
 
         nodes_from_point_list.iter()
+           .rev()
            .map(|metadata| metadata.node.to_untrusted_node_address())
            .collect()
     }

components/layout_thread/lib.rs

@@ -1160,7 +1160,7 @@ impl LayoutThread {
                                         .as_ref()
                                         .expect("Tried to hit test with no display list")
                                         .hit_test(&point, &rw_data.stacking_context_scroll_offsets);
-                    rw_data.hit_test_response = (result.get(0).cloned(), update_cursor);
+                    rw_data.hit_test_response = (result.last().cloned(), update_cursor);
                 },
                 ReflowQueryType::NodeGeometryQuery(node) => {
                     let node = unsafe { ServoLayoutNode::new(&node) };